ref-filter: add support for %(contents:lines=X)

In 'tag.c' we can print N lines from the annotation of the tag using
the '-n<num>' option. Copy code from 'tag.c' to 'ref-filter' and
modify it to support appending of N lines from the annotation of tags
to the given strbuf.

Implement %(contents:lines=X) where X lines of the given object are
obtained.

While we're at it, remove unused "contents:<suboption>" atoms from
the `valid_atom` array.

Add documentation and test for the same.

Mentored-by: Christian Couder <christian.couder@gmail.com>
Mentored-by: Matthieu Moy <matthieu.moy@grenoble-inp.fr>
Signed-off-by: Karthik Nayak <karthik.188@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 43 insertions, 4 deletions

diff --git a/ref-filter.c b/ref-filter.c
index f046d826bd..32aab37d36 100644
--- a/ref-filter.c
+++ b/ref-filter.c
@@ -45,9 +45,6 @@ static struct {
 	{ "subject" },
 	{ "body" },
 	{ "contents" },
-	{ "contents:subject" },
-	{ "contents:body" },
-	{ "contents:signature" },
 	{ "upstream" },
 	{ "push" },
 	{ "symref" },
@@ -65,6 +62,11 @@ struct align {
 	unsigned int width;
 };
 
+struct contents {
+	unsigned int lines;
+	struct object_id oid;
+};
+
 struct ref_formatting_stack {
 	struct ref_formatting_stack *prev;
 	struct strbuf output;
@@ -81,6 +83,7 @@ struct atom_value {
 	const char *s;
 	union {
 		struct align align;
+		struct contents contents;
 	} u;
 	void (*handler)(struct atom_value *atomv, struct ref_formatting_state *state);
 	unsigned long ul; /* used for sorting when not FIELD_STR */
@@ -643,6 +646,30 @@ static void find_subpos(const char *buf, unsigned long sz,
 	*nonsiglen = *sig - buf;
 }
 
+/*
+ * If 'lines' is greater than 0, append that many lines from the given
+ * 'buf' of length 'size' to the given strbuf.
+ */
+static void append_lines(struct strbuf *out, const char *buf, unsigned long size, int lines)
+{
+	int i;
+	const char *sp, *eol;
+	size_t len;
+
+	sp = buf;
+
+	for (i = 0; i < lines && sp < buf + size; i++) {
+		if (i)
+			strbuf_addstr(out, "\n    ");
+		eol = memchr(sp, '\n', size - (sp - buf));
+		len = eol ? eol - sp : size - (sp - buf);
+		strbuf_add(out, sp, len);
+		if (!eol)
+			break;
+		sp = eol + 1;
+	}
+}
+
 /* See grab_values */
 static void grab_sub_body_contents(struct atom_value *val, int deref, struct object *obj, void *buf, unsigned long sz)
 {
@@ -653,6 +680,7 @@ static void grab_sub_body_contents(struct atom_value *val, int deref, struct obj
 	for (i = 0; i < used_atom_cnt; i++) {
 		const char *name = used_atom[i];
 		struct atom_value *v = &val[i];
+		const char *valp = NULL;
 		if (!!deref != (*name == '*'))
 			continue;
 		if (deref)
@@ -662,7 +690,8 @@ static void grab_sub_body_contents(struct atom_value *val, int deref, struct obj
 		    strcmp(name, "contents") &&
 		    strcmp(name, "contents:subject") &&
 		    strcmp(name, "contents:body") &&
-		    strcmp(name, "contents:signature"))
+		    strcmp(name, "contents:signature") &&
+		    !starts_with(name, "contents:lines="))
 			continue;
 		if (!subpos)
 			find_subpos(buf, sz,
@@ -682,6 +711,16 @@ static void grab_sub_body_contents(struct atom_value *val, int deref, struct obj
 			v->s = xmemdupz(sigpos, siglen);
 		else if (!strcmp(name, "contents"))
 			v->s = xstrdup(subpos);
+		else if (skip_prefix(name, "contents:lines=", &valp)) {
+			struct strbuf s = STRBUF_INIT;
+			const char *contents_end = bodylen + bodypos - siglen;
+
+			if (strtoul_ui(valp, 10, &v->u.contents.lines))
+				die(_("positive value expected contents:lines=%s"), valp);
+			/*  Size is the length of the message after removing the signature */
+			append_lines(&s, subpos, contents_end - subpos, v->u.contents.lines);
+			v->s = strbuf_detach(&s, NULL);
+		}
 	}
 }